Def or DEF may refer to:
Defamation—also calumny, vilification, and traducement—is the communication of a false statement that harms the reputation of an individual person, business, product, group, government, religion, or nation.
Deforestation, clearance or clearing is the removal of a forest or stand of trees where the land is thereafter converted to a non-forest use.
Defibrillation is a treatment for life-threatening cardiac dysrhythmias, specifically ventricular fibrillation (VF) and non-perfusing ventricular tachycardia (VT).
The Defence Research and Development Organisation (DRDO) is an agency of the Republic of India, charged with the military's research and development, headquartered in New Delhi, India.
The 2015 AFC Championship Game football tampering scandal, commonly referred to as Deflategate, was a National Football League (NFL) controversy involving the allegation that the New England Patriots tampered with footballs used in the American Football Conference (AFC) Championship Game against the Indianapolis Colts on January 18, 2015. The league announced on May 11, 2015, that it would suspend Patriots quarterback Tom Brady for four games of the 2015 regular season for his alleged part in the scandal.
The Defenders is a set of fictional superhero groups with fluctuating membership appearing in American comic books published by Marvel Comics.
The Deficit Reduction Act of 2005 is a United States Act of Congress concerning the federal budget that became law in 2006.
Def Leppard are an English rock band formed in 1977 in Sheffield as part of the new wave of British heavy metal movement.
In economics, deflation is a decrease in the general price level of goods and services. Deflation occurs when the inflation rate falls below 0% (a negative inflation rate).